1. Field of the Invention
This invention relates to a method of producing combustion chambers for liquid propellant rocket engines and particularly it relates to a method of producing combustion chambers of the type having a channel construction for cooling purposes.
2. Description of the Prior Art
In recent years, in liquid propellant rocket engines, there has been a demand for higher thrust, with the result that the cooling and pressure resistance of the combustion chamber have become important problems. In a conventional liquid propellant rocket engines, the combustion chamber is provided with a cooling wall of channel construction to satisfy these cooling and pressure resistance requirements. FIGS. 1 and 2 are a schematic perspective view and a cross section, respectively, of a conventional rocket engine chamber. As is clear from FIG. 2, the combustion chamber 1 comprises an inner cylinder 2 made of a high-thermal conductivity material, such as copper or a copper alloy, and an outer cylinder 3 joined to said inner cylinder 2. The periphery of the inner cylinder 2, as is clear from FIG. 2, is formed with a plurality of grooves 4, which constitutes a cooling section of channel construction; liquid hydrogen, for example, is passed through these grooves 4 to cool the combustion chamber 1.
In this connection, the combustor 1 described above has heretofore been produced, as shown in FIGS. 3 through 5 depicting fragmentary perspective views, by preparing the inner cylinder 2, machining the outer periphery of the inner cylinder 2 to form the grooves 4, and joining the outer cylinder 3 to the periphery of the inner cylinder 2. However, since the rocket combustor 1 will be subjected to very high pressures, the inner and outer cylinders 2 and 3 must be joined together very strongly.
Thus, for joining the inner and outer cylinders 2 and 3 together, there have heretofore been tried various methods such as brazing, electroforming, powder metallurgy, and diffusion bonding. However, in brazing, if the fluidity of the brazing material is poor, there has been a disadvantage that uniform joining strength cannot be obtained. Further, in the case of electroforming, since it is used to form an outer cylinder by Ni-electroplating, there has been a problem that the electrolysis reaction takes a long time. Further, when the diffusion bonding method is used, the bonding accuracy obtained has been found to be poor.
On the other hand, U.S. patent application Ser. No. 686,618 and U.S. Pat. No. 4,508,680 disclose methods of joining inner and outer cylinders by powder metallurgy. According to these prior arts, the production method comprises preparing an inner cylinder provided at its outer periphery with a cooling wall of channel construction having a plurality of grooves, filling the grooves of the inner cylinder with paraffin wax or a mixture of paraffin wax and Al.sub.2 O.sub.3 powder, and compression molding a metal powder placed around the periphery of the inner cylinder filled with said filler, under isostatic pressure to a predetermined thickness to thereby form an outer cylinder.
If it is produced by this method, it is necessary to form a gas-impermeable truly dense sintered layer to prevent leakage of the cooling agent. Thus, a copper powder compacted layer having a high molding density must be produced under high pressure and the copper layer thickness must be increased, leading to a drawback that the production method and conditions are severe.